JPH0714130A - Rotary drum device - Google Patents

Abstract

PURPOSE:To press a rotary drum against a fixed drum with a prescribed load without generating an eddy current in a motor yoke and to reduce the size of a device by providing an attracting magnetic circuit constituted of an attracting magnet and an attracting plate. CONSTITUTION:An attracting yoke 35 and the attracting magnet 36 are integrally stuck to a fixed drum 1, an attracting plate 38 is fixed to a rotary drum 9 through a spacer 37 and an attracting force is generated between both the drums with this attracting magnetic circuit. On the other hand, a magnetic circuit is constituted of a motor magnet 18, a rotor yoke 16 and a back yoke 23. When the current is allowed to flow through a stator coil 21, an electromagnetic force is generated in a motor rotor 19 since a magnetic flux runs through a stator coil 21 in the drum 9 and then the drum 9 is rotated. At this time, the eddy current is not generated in the yoke 23 since the rotor 19 and the yoke 23 are fixed to the drum 9. Further, the magnetic field of the attracting magnetic circuit does not affect a magnetic head 11 since the attracting yoke 35 is stuck to the attracting magnet 36. Therefore, size of the device can be also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing information on / from a magnetic tape such as VTR or DAT. In recent years, there is a strong demand for miniaturization and improvement of recording density in the magnetic recording / reproducing apparatus. In the rotating drum device, which is one of the mechanical components that make up the magnetic recording / reproducing device, the axial size is reduced, the diameter of the rotating drum is reduced,
Higher rotation speed, higher performance of magnetic head and rotary transformer, and lower noise are desired. The present invention relates to a rotary drum device that satisfies the above needs.

[0002]

2. Description of the Related Art FIG. 12 shows, for example, JP-A-63-3116.
19, JP-A-2-90136 and JP-A-3-2256.
14 is a sectional view of a conventional rotary drum device shown in FIG.
FIG. 13 is a sectional view of another conventional rotary drum device disclosed in, for example, Japanese Patent Laid-Open No. 2-42616.

In FIG. 12 showing a conventional apparatus, 1 is a fixed drum, 2 is a lead for guiding a magnetic tape formed on the outer peripheral surface of the fixed drum 1, and 3 is a fixed drum by a method such as shrink fitting or press fitting. It is an axis provided at the center of 1. Reference numeral 4 is an inner race formed on the shaft 3, 5 is an outer race formed with an outer race corresponding to the inner race 4, 6 is a steel ball located between the shaft 3 and the outer race 5, and supporting a rotating portion. 5 and the steel ball 6 constitute a shaft integrated bearing 7. Reference numeral 8 is a rotary member fixed to the outer ring 5, 9 is a rotary drum fixed to the rotary member 8 with a screw 10, 11 is a magnetic head fixed to the rotary drum 9 with a screw 12, and 13 is screwed to the rotary drum 9. It is a step adjusting screw whose end is in contact with the flat surface of the magnetic head 11.

A rotary rotary transformer 14 is fixed to the rotary member 8 by a method such as adhesion, and is electrically connected to the magnetic head 11. Reference numeral 15 denotes a fixed-side rotary transformer fixed to the fixed drum 1 by a method such as adhesion, which is paired with the rotary-side rotary transformer 14.

Reference numeral 16 is a rotor yoke fixed to the rotary drum 9 with screws 17, and reference numeral 18 is a motor magnet fixed to the rotor yoke 16. The rotor yoke 16 and the motor magnet 18 constitute a motor rotor 19. 20
Is a bush fixed to the shaft 3, 21 is a stator coil fixed to the bush 20 with a screw 22, and is arranged facing the motor magnet 18. Reference numeral 23 is a back yoke fixed to the rotary drum 9.
The stator coil 21 is placed between the motor rotor 3 and the motor rotor 18.

Next, the operation of the conventional apparatus shown in FIG. 12 will be described. A magnetic circuit is formed between the motor rotor 19 and the back yoke 23 in the rotary drive motor formed in the rotary drum 9, and when a current is passed through the stator coil 21, the motor rotor 19 and the back yoke 23 are electromagnetically moved in a rotating direction. A force is generated, and the rotating drum 9 rotates about the shaft 3 as a center of rotation. At this time, since the motor rotor 19 and the back yoke 23 both rotate while being fixed to the rotary drum 9, the relative positional relationship between them does not change, so that no eddy current is generated in the back yoke 23 and the efficiency of the motor is improved. good. In addition, the shaft-integrated bearing 7 is preloaded in the thrust direction and the radial direction with the rotating member 8
Is fixed, the rotational trajectory of the magnetic head 11 does not deviate from a predetermined position even if an external impact is applied to the device in the thrust direction.

When information is recorded on the magnetic tape, when a current related to the recording information is passed through the fixed rotary transformer 15, a recording current is passed through the rotary rotary transformer 14 to the magnetic head 11 to lead 2. Information is recorded on a magnetic tape (not shown) running while being guided. When reproducing the information recorded on the magnetic tape, the information can be obtained by the reverse route of the recording.

Since the conventional rotary drum device is constructed as described above, when it is used at a high speed, there are problems that vibration and noise mainly due to the bearing are large and the life is short.

In order to solve the above problems of the conventional device, another conventional device adopting a fluid bearing as a bearing is a rotary drum device shown in FIG. In the figure, the same or corresponding parts as those of the conventional device are designated by the same reference numerals. In FIG. 13, 1 is a fixed drum, 2 is a lead formed on the outer peripheral surface of the fixed drum 1, 3 is a shaft provided at the center of the fixed drum 1 by a method such as shrink fitting or press fitting, and 24 is a shaft. Three
A radial fluid bearing 9 is formed on the outer peripheral surface of the rotary drum 9, a rotary drum 9 having the shaft 3 as the center of rotation via the radial fluid bearing 24, and a magnetic head 11 fixed to the rotary drum 9 by screws 12.

A rotary rotary transformer 14 is fixed to the rotary drum 9 by an adhesive method or the like, and is electrically connected to the magnetic head 11. Reference numeral 15 is a fixed-side rotary transformer fixed to the fixed drum 1 by a method such as adhesion, and 25 is a thrust-direction fluid bearing fixed to the rotating drum 9 and facing the end surface of the shaft 3.

Reference numeral 16 denotes a rotor yoke fixed to the rotary drum 9 together with a thrust direction fluid bearing 25 by a screw 26,
A motor magnet 18 is fixed to the rotor yoke 16 coaxially with the rotor yoke 16. The rotor yoke 16 and the motor magnet 18 constitute a motor rotor 19.
Reference numeral 27 is a stator base fixed to the fixed drum 1 with screws 28, 29 is a stator yoke fixed to the stator base 27 with screws 30, 31 is a stator coil fixed onto the stator yoke 29 by a method such as bonding, The stator yoke 29 and the stator coil 31 constitute a motor stator 32.

Next, the operation of another conventional apparatus shown in FIG. 13 will be described. In the rotary drive motor configured above the rotary drum 9, the motor rotor 19 and the motor stator 3
A magnetic circuit is formed between the two, and the stator coil 31
When a current is applied to the motor rotor 19, an electromagnetic force is generated in the direction in which the motor rotor 19 is rotated, and the rotary drum 9 rotates about the shaft 3 as the center of rotation. Grease is usually enclosed between the shaft 3 and the rotary drum 9, and dynamic pressure is generated between the shaft 3 and the rotary drum 9 by the radial fluid bearing 24, so that the rotary drum 9 is supported with respect to the shaft 3.

Further, an attractive force is generated between the motor magnet 18 and the stator yoke 29, and the rotating portion integrated with the motor magnet 18 is attracted to the fixed drum 1 side. On the other hand, grease is usually filled between the thrust direction hydrodynamic bearing 25 and the end surface of the shaft 3 on the rotary drum 9 side, and as the rotary drum 9 rotates, dynamic pressure is also generated in the thrust direction. As a result, the attractive force between the motor magnet 18 and the stator yoke 29 and the self-weight of the entire rotating portion are balanced with the dynamic pressure generated by the thrust direction fluid bearing 25, and the rotating drum 9 is supported in the thrust direction of the shaft 3.

Since the conventional rotary drum device shown in FIG. 13 is configured as described above, the eddy current generated in the stator yoke 29 with the rotation of the motor magnet 18 increases as the rotational speed of the rotary drum 9 increases. However, there is a problem that so-called iron loss increases and the efficiency of the motor deteriorates.

[0015]

Since the conventional rotary drum device is constructed as described above, when a bearing using steel balls is adopted, there is a problem that vibration and noise increase at high speed. Further, when the fluid bearing is adopted, it is necessary to suck the rotating portion to the fixed portion, and there is a problem that the motor efficiency deteriorates when the motor including the stator yoke 29 and the motor rotor 19 is used.

The present invention has been made to solve the above problems, and an object thereof is to obtain a small-sized high-performance rotary drum device compatible with high-speed rotation.

[0017]

A rotary drum device according to the present invention includes a fixed drum, a rotary drum which is supported by the fixed drum, and on which a magnetic head is mounted, and which is supported on one of the fixed drum side and the rotary drum side. An attraction magnet disposed in the vicinity of a portion where the fixed drum and the rotating drum face each other, and is supported on a drum side different from the side on which the attraction magnet is supported and is disposed to face the attraction magnet. An attraction plate is provided, and the attraction magnetic circuit is configured by the attraction magnet and the attraction plate.

According to the present invention, in addition to the above means, when the attraction magnet is supported on the fixed drum side, the attraction magnet is supported on the rotating drum side between the attraction magnet and the fixed drum. In this case, an attraction yoke is provided on the surface of the attraction magnet facing the magnetic head.

Further, according to the present invention, a fixed drum, a rotary drum supported by the fixed drum, on which a magnetic head is mounted, a stator coil fixed to the fixed drum side, a stator coil fixed to the rotary drum side, and the stator coil In a rotary drum device composed of a motor rotor and a back yoke positioned so as to sandwich the magnetic disk, a suction magnetic circuit is formed by a suction magnet arranged on the fixed drum side and a suction plate arranged on the rotary drum side. The rotary drum is configured to suck the rotary drum toward the fixed drum.

Further, the present invention is characterized in that an attraction yoke is fixed to the attraction magnet on the side away from the magnetic head.

Further, according to the present invention, there are provided a fixed drum, a rotary drum supported by the fixed drum and having a magnetic head mounted thereon, a stator coil fixed to the fixed drum side, and a stator coil fixed to the rotary drum side. In a rotary drum device composed of a motor rotor and a back yoke positioned so as to be sandwiched, an attracting magnet disposed on the rotating drum side, an attracting yoke fixed to the magnetic head side of the attracting magnet, and the fixed drum. A suction magnetic circuit is constituted by the suction plate disposed on the side, and the rotary drum is suctioned to the fixed drum side.

Further, according to the present invention, a fixed drum, a rotary drum supported by the fixed drum and having a magnetic head mounted thereon, a stator coil fixed to the fixed drum side, and a stator coil fixed to the rotary drum side are provided. In a rotary drum device composed of a motor rotor and a back yoke positioned so as to be sandwiched, on the rotary drum side, adsorptions alternately arranged with the magnetic heads in the drum circumferential direction on substantially the same plane as the magnetic heads. A magnetic circuit for attraction is constituted by a magnet and an attraction plate arranged on the fixed drum side, and the rotary drum is attracted to the fixed drum side.

Further, the present invention is characterized in that the attraction magnet is provided with an attraction yoke. Further, an attraction yoke is fixed to this attraction magnet.

[0024]

According to the rotary drum device of the present invention, the rotary drum can be reliably pressed against the fixed drum with a predetermined load without providing an extra space.

Further, since the attraction yoke is fixed to the attraction magnet, this magnetic force hardly affects the magnetic head.

Further, since the magnetic circuit for attraction is provided in addition to the magnetic circuit for driving the rotary drum, no eddy current is generated inside the motor yoke, and moreover, the rotary drum is securely fixed to the fixed drum under a predetermined load. Can be pressed.

[0027]

【Example】

Example 1. 1 is a sectional view of a rotary drum device of the present invention, FIG. 2 is a schematic assembly diagram of the rotary drum device of FIG. 1, FIG. 3 is a diagram showing a correlation between an external magnetic field at a magnetic head position and an inductance of the magnetic head, FIG. 4 and 5 are diagrams showing the magnetic flux in the vicinity of the magnetic head. In the figure, the same or corresponding parts as those of the conventional device are designated by the same reference numerals.

In the figure, 1 is a fixed drum, 2 is a lead for guiding a magnetic tape formed on the outer peripheral surface of the fixed drum 1, and 3 is provided at the center of the fixed drum 1 by a method such as shrink fitting or press fitting. Shaft, 24 is a radial fluid bearing formed on the outer peripheral surface of the shaft 3, 9 is a rotary drum having the shaft 3 as the center of rotation via the radial fluid bearing 24, 1
Reference numeral 1 denotes a magnetic head fixed to a rotating drum 9 by screws 12, and 13 denotes a magnetic head having an end portion screwed into the rotating drum 9.
It is a step adjusting screw that is in contact with the flat portion of No. 1.

A rotary rotary transformer 14 is fixed to the rotary drum 9 by a method such as adhesion, and is electrically connected to the magnetic head 11. Reference numeral 15 denotes a fixed-side rotary transformer that is fixed to the fixed drum 1 by a method such as adhesion and forms a pair with the rotary-side rotary transformer 14. Reference numeral 25 denotes a thrust direction fluid bearing fixed to the fixed drum 1, and faces the end portion 9a of the rotating drum 9.

Reference numeral 16 is a rotor yoke fixed to the rotating drum 9 by screws 17, and reference numeral 18 is a motor magnet fixed to the rotor yoke 16 coaxially with the rotor yoke 16. The rotor yoke 16 and the motor magnet 18 constitute a motor rotor 19. Reference numeral 20 is a bush that is in contact with the shaft 3, and 21 is a stator coil that is formed of a sheet-shaped coil that is fixed to the shaft 3 together with the bush 20 by a screw 34, and is arranged so as to face the motor magnet 18.
Reference numeral 23 is a back yoke fixed to the rotary drum 9, and has a positional relationship in which the stator coil 21 is arranged between the back yoke 23 and the motor rotor 19.

Reference numeral 35 is an attraction yoke fixed to the fixed drum 1, 36 is an attraction magnet integrally fixed to the attraction yoke 35, 37 is a spacer abutting on the rotating drum 9, and 38
Is a suction plate which is in contact with the spacer 37 and fixed to the rotary drum 9 via the spacer 37 by the screw 39, and constitutes a suction magnetic circuit together with the suction yoke 35 and the suction magnet 36.

As the rotary rotary transformer 14 and the fixed rotary transformer 15, cylindrical rotary transformers are used so as to facilitate the miniaturization of the apparatus when the number of channels is increased.

Next, the operation of the rotary drum device will be described. Motor magnet 18 and rotor yoke 1
6 and the back yoke 23 constitute a magnetic circuit, and the magnetic flux penetrates the stator coil 21 which is the fixed portion. When a current is applied to the stator coil 21, an electromagnetic force is generated in the direction in which the motor rotor 19 is rotated, and as a result, the rotating drum 9 is rotated.
Rotates about the shaft 3. At this time, since the motor rotor 19 and the back yoke 23 both rotate while being fixed to the rotating drum 9, the relative positional relationship between them does not change, and no eddy current is generated in the back yoke 23.

Since the rotation driving magnetic circuit is constructed as described above, no magnetic force is generated between the motor magnet 18 and the stator coil 21 to attract the rotating drum 9 to the fixed drum 1. However, the attraction magnetic circuit composed of the attraction yoke 35 fixed to the fixed drum 1, the attraction magnet 36, and the attraction plate 38 fixed to the rotating drum 9 causes attraction force between the rotating drum 9 and the fixed drum 1. Occurs. The suction force is supported by the thrust direction fluid bearing 25. It is possible to install this magnetic circuit for suction in the lower part of the fluid bearing, but it is necessary to newly provide a space, the device may become large in the height direction and the width direction, and the assembly process of the device becomes complicated. There is also a fear of becoming. The present invention, in which the magnetic circuit for attraction is provided in the vicinity of the facing portion of the rotary drum 9 and the fixed drum 1, can realize downsizing of the device without such a problem, and the assembly is simple.

On the other hand, in order to reduce the size of the device, the arrangement of parts in the device becomes very dense, and the distance between the attraction magnet 36 and the magnetic head 11 must be very close. When an external magnetic field is present near the magnetic head 11, the magnetic head 11
Does not have the desired characteristics due to the influence of the external magnetic field. FIG. 3 shows an example of the relationship between the head inductance, which is one index showing the performance of the magnetic head 11, and the external magnetic field near the magnetic head. In order to secure the required inductance of the magnetic head 11, the magnetic head 11 is required. It can be seen that the magnetic field in the vicinity must be suppressed below a certain value. That is, when the magnetic circuit for attraction is arranged near the magnetic head 11, the magnetic field of the magnetic circuit for attraction causes the magnetic head 11 to move.
It is necessary to take measures so as not to affect the.

An example of the result obtained by analyzing the magnetic flux lines in the axial cross section of the space near the magnetic circuit in the magnetic circuit for attraction having the attracting plate 38 and the attracting magnet 36 as a basic structure is shown in FIG. FIG. 4 shows the result of the case of sticking, and FIG. 5 shows the result of the case without the suction yoke. Here, it is assumed that the attraction magnet 36 is a rare earth element, and the attraction plate 38 and the attraction yoke 35 are iron-based materials. Further, in the figure, a point A represents a position where the magnetic head 11 is placed. It can be said that the strength of the magnetic field at an arbitrary position is stronger as the number of magnetic flux lines in the space having the predetermined cross-sectional area, that is, the magnetic flux line density is larger. The magnetic flux line density in the vicinity of the point A is lower when the suction yoke 35 is present than when the suction yoke 35 is not provided. That is, it can be understood that fixing the attraction yoke 35 to the attraction magnet 36 is an effective means for reducing the leakage magnetic flux from the attraction magnetic circuit to the magnetic head 11.

Example 2. In the first embodiment, the suction plate 38
Although the case where the attraction magnet 36 is fixed to the rotating portion and the attraction magnet 36 is fixed to the fixed portion has been described, the case where the attraction magnet 36 is fixed to the rotating portion and the attraction plate 38 is fixed to the fixing portion will be described below. Second Embodiment FIG. 6 is a sectional view of a rotary drum device showing a second embodiment of the present invention.

In the figure, 11 is a magnetic head fixed to the rotary drum 9, 37 is a spacer contacting the rotary drum 9, 38 is a suction plate fixed to the fixed drum 1 by a method such as adhesion, and 36 is a suction plate. An attraction magnet arranged so as to face 38, 35 is an attraction yoke fixed to a surface of the attraction magnet 36 close to the magnetic head 11, and the attraction magnet 36 and the attraction yoke 35 are rotated by a screw 39 via a spacer 37 with a rotary drum. It is fixed at 9. The attraction yoke 35, the attraction magnet 36, and the attraction plate 38 constitute a attraction magnetic circuit. The configuration other than this magnetic circuit for attraction is the same as that of the first embodiment shown in FIG.

Next, the operation will be described. In the configuration shown in FIG. 6, the rotary drum 9 is attracted toward the fixed drum 1 by the magnetic circuit for attraction composed of the attraction magnet 36 and the attraction plate 38, and the same operation as that of the first embodiment shown in FIG. 1 is performed. It is clear to get.

Further, in the configuration shown in FIG. 6, since the magnetic head 11 and the attraction magnet 36 are close to each other, by placing the attraction yoke 35 on the side surface of the attraction magnet 36 on the magnetic head 11 side, the attraction magnetic circuit is provided. The magnetic flux leaking from the magnetic head does not affect the magnetic head 11.

Example 3. In the above-mentioned first and second embodiments, the case where the magnetic circuit for attraction is arranged below the magnetic head 11 has been described.
The case where they are arranged in substantially the same plane as 1 will be described below. 7 is a cross-sectional view of a rotary drum device showing a third embodiment of the present invention, FIG. 8 is a plan view of a rotating part of the rotary drum device shown in FIG. 7 as seen from the mounting direction of the magnetic head 11, and FIG.
FIG. 3 is a schematic assembly view of the rotary drum device of FIG.

In the figure, 11 is a rotary drum 9 and 180
° magnetic head mounted opposite by screws 12,
Reference numeral 40 is a fan-shaped attraction magnet, and 41 is a screw for fixing the attraction magnet 40 to the rotary drum 9. As shown in FIG. 8, the attracting magnets 40 are mounted 180 ° apart from each other at a position offset by 90 ° from the mounting direction of the magnetic head 11.

Reference numeral 38 denotes an annular attracting plate attached to the fixed drum 1, which is arranged at a predetermined distance from the attracting magnet 40, and the attracting magnet 40 and the attracting plate 38 form a magnetic circuit for attraction. There is. The configuration other than this magnetic circuit for attraction is the same as that of the first embodiment shown in FIG.

Next, the operation will be described. In the configuration shown in FIG. 7, the rotary drum 9 is fixed to the fixed drum 1 by the magnetic circuit for attraction including the attraction magnet 40 and the attraction plate 38.
It is obvious that the same effect as in Example 1 shown in FIG.

Further, since the strength of the magnetic field at an arbitrary position is inversely proportional to the square of the distance from the magnetic field source, the magnetic circuit for attraction may be formed directly below the magnetic head 11 as shown in FIG. By alternately arranging the magnetic heads 11 and the attraction magnets 40 in the circumferential direction of the rotary drum 9 as shown by, the distance between the magnetic heads 11 and the attraction magnetic circuit can be increased, and the external magnetic field near the magnetic heads 11 can be reduced. Can be suppressed. Further, it is possible to further effectively use the space in the device.

Example 4. In the rotary drum device shown in the third embodiment, as shown in FIG.
If the attracting yoke 42 is fixed to the surface of the rotating drum 9 which is close to the magnetic head 11 in the circumferential direction, the leakage magnetic flux of the magnetic circuit for attraction to the magnetic head 11 can be further reduced.

Example 5. In the embodiment shown in FIGS. 1, 6 and 7, the shaft 3 is fixed to the fixed drum 1 and a fluid bearing is adopted as a bearing for supporting the rotating drum 9 in both the radial direction and the thrust direction. The shaft may rotate, or a steel ball may be used for the bearing. The case where the shaft rotates and a steel ball is used for the thrust direction bearing will be described below. 11 is a sectional view of a rotary drum device showing a fifth embodiment of the present invention.

In the figure, 1 is a fixed drum, 9 is a rotary drum arranged coaxially with the fixed drum 1, 11 is a magnetic head fixed to the rotary drum 9, 43 is a fixed drum 1 coaxially with the fixed drum 1. , A steel ball fixed to the bush 43, a 45 contacting the steel ball 44 at one end, and concentrically fixed to the rotating drum 9 by a method such as shrink fitting and press fitting near the other end surface. Axis, 24 is axis 4
5 is a radial fluid bearing provided in FIG.

Reference numeral 16 is a rotor yoke fixed to the rotary drum 9 by screws 17, and reference numeral 18 is a motor magnet fixed to the rotor yoke 16 coaxially with the rotor yoke 16. The rotor yoke 16 and the motor magnet 18 constitute a motor rotor 19. Reference numeral 23 denotes a back yoke fixed to the rotary drum 9 so as to face the motor rotor 19, and 27
Is a stator base fixed to the fixed drum 1 with screws 28, 21 is a stator coil composed of a sheet-shaped coil fixed to the stator base 27 with screws 30, and this stator coil 21 is composed of the motor rotor 19 and the back yoke 23. There is a positional relationship that is arranged between them.

Reference numeral 35 is an attraction yoke fixed to the fixed drum 1, 36 is an attraction magnet integrally fixed to the attraction yoke 35, 37 is a spacer abutting on the rotating drum 9, and 38.
Comes into contact with the spacer 37, and the spacer 37 is fixed by the screw 39.
The attraction plate fixed to the rotary drum 9 via the suction yoke 35 and the attraction magnet 36 constitutes an attraction magnetic circuit. Note that other configurations are the same as the configurations of the first embodiment shown in FIG.

Next, the operation will be described. As in the first embodiment, the rotary driving magnetic circuit constituted by the motor rotor 19, the back yoke 23, and the stator coil 21 rotates the rotary drum 9 about the shaft 45 without eddy current loss. The shaft 45 is fixed to the rotary drum 9, and the shaft 45 also rotates as the rotary drum 9 rotates. Grease is usually enclosed between the shaft 45 and the fixed drum 1. As the shaft 45 rotates, a dynamic pressure is generated between the shaft 45 and the fixed drum 1, and the rotary drum 9 passes through the shaft 45 with respect to the fixed drum 1. Supported.

The attraction magnet 36 and the attraction plate 3
The rotary drum 9 is attracted to the fixed drum 1 side by the magnetic circuit for attraction constituted by 8. At this time, one end of the shaft 45 contacts the steel ball 44 fixed to the fixed drum 1 via the bush 43 to determine the height of the magnetic head 11, and the steel ball 44 serves as a pivot bearing and uses the shaft 45 in the thrust direction. To support.

[0053]

As described above, according to the present invention, the magnetic circuit for attraction can be installed without providing an extra space, the device can be downsized, and the attraction magnet and the attraction plate can be used. The attraction force reliably presses the rotating drum against the fixed drum with a predetermined load, and the height of the magnetic head can be kept stable. Further, since the magnetic circuit for attraction is provided separately from the magnetic circuit for driving the rotary drum, the rotary drum is pressed against the fixed drum with a predetermined load without generating an eddy current inside the motor yoke.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary drum device showing a first embodiment of the present invention.

FIG. 2 is a schematic assembly view of the rotary drum device of FIG.

FIG. 3 is a diagram showing a correlation between an external magnetic field at a magnetic head position and an inductance of the magnetic head.

FIG. 4 is a diagram showing a magnetic flux in the vicinity of a magnetic circuit for attraction when an attraction yoke is fixed to an attraction magnet.

FIG. 5 is a diagram showing magnetic flux in the vicinity of a magnetic circuit for attraction when an attraction yoke is not attached to the attraction magnet.

FIG. 6 is a sectional view of a rotary drum device showing a second embodiment of the present invention.

FIG. 7 is a sectional view of a rotary drum device showing a third embodiment of the present invention.

8 is a plan view of a rotating portion of the rotary drum device shown in FIG. 7, as viewed from a magnetic head mounting direction.

9 is a schematic assembly view of the rotary drum device of FIG. 7.

10 is another embodiment of the attraction magnet of the rotary drum device of FIG.

FIG. 11 is a sectional view of a rotary drum device showing a fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view of a conventional rotary drum device.

FIG. 13 is a cross-sectional view of another conventional rotary drum device.

[Explanation of symbols]

 1 Fixed Drum 9 Rotating Drum 11 Magnetic Head 19 Motor Rotor 21 Stator Coil 23 Back Yoke 35 Adsorption Yoke 36 Adsorption Magnet 38 Adsorption Plate In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (7)

[Claims] 1. A fixed drum, a rotary drum supported by the fixed drum, and having a magnetic head mounted thereon, and one of the fixed drum side and the rotary drum side supported, and the fixed drum and the rotary drum face each other. The attraction magnet and the attraction plate, the attraction magnet being disposed in the vicinity of the portion, and the attraction plate being supported on the side where the attraction magnet is supported and the drum side different from the one supported by the attraction magnet and facing the attraction magnet. A rotary drum device, in which a magnetic circuit for suction is configured by. 2. A magnetic head of the attraction magnet between the attraction magnet and the fixed drum when the attraction magnet is supported on the fixed drum side, and when the attraction magnet is supported on the rotating drum side. The rotary drum device according to claim 1, wherein a suction yoke is provided on a surface facing to. 3. A fixed drum, a rotary drum supported by the fixed drum, on which a magnetic head is mounted, a stator coil fixed on the fixed drum side, fixed on the rotary drum side, and sandwiching the stator coil. In a rotary drum device composed of a motor rotor and a back yoke located, a suction magnetic circuit is constituted by a suction magnet arranged on the fixed drum side and a suction plate arranged on the rotary drum side. A rotary drum device, wherein the rotary drum is sucked toward the fixed drum side. 4. The rotary drum device according to claim 3, wherein an attraction yoke is fixed to the attraction magnet on the side away from the magnetic head. 5. A fixed drum, a rotary drum supported by the fixed drum and having a magnetic head mounted thereon, a stator coil fixed to the fixed drum side, and fixed to the rotary drum side so as to sandwich the stator coil. In a rotary drum device composed of a motor rotor and a back yoke, a suction magnet disposed on the rotary drum side, a suction yoke fixed to the magnetic head side of the suction magnet, and a fixed drum side. A magnetic circuit for attraction is constituted by the attracted suction plate, and the rotary drum attracts the rotary drum to the fixed drum side. 6. A fixed drum, a rotary drum supported by the fixed drum, on which a magnetic head is mounted, a stator coil fixed to the fixed drum side, and fixed to the rotary drum side so as to sandwich the stator coil. In the rotary drum device composed of the motor rotor and the back yoke, the attracting magnets arranged alternately on the rotary drum side in the drum circumferential direction on the rotary drum side in substantially the same plane as the magnetic head; A rotary drum device, wherein a suction magnetic circuit is constituted by a suction plate arranged on the fixed drum side, and the rotary drum is sucked to the fixed drum side. 7. The rotary drum device according to claim 4, wherein the attraction magnet is provided with an attraction yoke.